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Lab Manual for Moffitt-Long and Mount Zion

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Creatinine, Serum / Plasma

Item Value
Approval req'd? No
Available Stat? Yes
Test code CRG
Test group Creatinine
Performed by Parnassus & Mt. Zion Chemistry
In House Availability Test available 24 hours per day 7 days per week
Method Spectrophotometric, kinetic (alkaline picrate,Jaffe) assay on Beckman DXC 600/800 analyzers. Calibration traceable to isotope dilution mass spec (IDMS) standardization

Click here for more information on Parnassus assay

Click here for more information on MtZ assay
Container type Gold top or Light Green top
Amount to Collect 1 mL blood Click here for Microdetermination info
Sample type Serum or plasma
Preferred volume 0.5 mL serum or plasma
Min. Volume 0.2 mL serum or plasma Click here for Microdetermination info
Units Creatinine: mg/dL, eGFR in mL/min/1.73 m2
Normal range Creatinine:
Age Male Female
< 1 year 0.30-0.70 mg/dL 0.30-0.70 mg/dL
1-18 years 0.30-0.90 mg/dL 0.30-0.90 mg/dL
≥ 19 years 0.71-1.22 mg/dL 0.52-1.06 mg/dL


eGFR:
≥ 18 years > 60 mL/min/1.73 m2
< 18 years Not calculated (See Addtl. Info.)


1. Pediatric reference ranges adapted from Beckman's published "Pediatric Reference Range Guidelines for Synchron Systems, Bulletin 9345.
2. Normal range for adults was determined by testing 270 male and female healthy blood donors at UCSF.
Synonyms GFR; eGFR; glomerular filtration rate
Stability Room temperature 8 hours, refrigerated 2 days, frozen at -20C 1 week
Turn around times STAT 1 hour, Routine 4 hours
Additional information To convert mg/dL to µmol/L (SI units) multiply by 88.4.

Ketones may artifactually increase results. Small to moderate ketones (40-80 mg/dl acetoacetic acid) may increase creatinine results by approx. 0.5 mg/dL; large amounts (> 125 mg/dL acetoacetic acid) may increase results approx 1 mg/dL, and very large amounts (> 400-500 mg/dL) may increase results more than 3 mg/dL.

Estimated GFR (eGFR) is reported with serum creatinine results in adults and is determined using the Modification of Diet in Renal Disease (MDRD) formula (traceable to isotope dilution mass spec IDMS calibration):

eGFR (mL/min/1.73 m2) = 175 x (Scr)-1.154 x (Age)-0.203 x (0.742 if female) x (1.212 if African American)

Because the MDRD formula is not considered sufficiently accurate for estimating GFR in patients with normal or mildly reduced renal function, results greater than 60 mL/min/1.73 meters squared body surface area are displayed as > 60 mL/min and are not reported as an exact number. Note that the estimated GFR result is not reliable in certain groups including severely ill patients. The MDRD equation used to estimate GFR has been validated only in Caucasian and African Americans 18 – 70 years of age. The equation has not been validated in other population groups, pregnant women, transplant recipients, medically unstable patients including those with acute renal failure, or in persons with extremes of body size, muscle mass, or nutritional status. Application of the MDRD calculation in these cases may lead to errors in GFR estimation. Click here for more information on this topic


GFR can also be estimated from serum creatinine in adults by the older formula of Cockcroft DW, Gault MH: (Nephron 1976;16:31) :


                 (140-age [years]) x (wt [kg]) 
GFR [mL/min] =   --------------------------- 
                  (72 x creatinine [mg/dL]) 



For women, multiply the calculated result by 0.85


Note that the Cockcroft-Gault formula is susceptible to many of the same limitations of the MDRD formula and may overestimate GFR by 16% or more when using current methods of creatinine measurement.


According to the National Kidney Disease Education Program, the best equation for estimating glomerular filtration rate (GFR) from serum creatinine in children is the Bedside Isotope Dilution Mass Spectrometry (IDMS)-traceable Schwartz equation
http://www.nkdep.nih.gov/lab-evaluation/gfr-calculators/children-conventional-unit.shtml

Bedside IDMS-traceable Schwartz Equation for Children

GFR (mL/min/1.73 m2) = (0.41 x Height in cm) / Creatinine in mg/dL)
CPT coding 82565
LOINC code 2160-0
Last Updated 10/4/2013 10:06:11 PM
Entry Number 265
Lab Procedure Link Click here for Procedure
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